This invention relates to a wooden frame for a grand piano, and more particularly relates to improvement in tone generating function of a wooden frame used for a grand piano.
In construction of a grand piano, a wooden frame functions as a support for a cast plate and, as a consequence, is required to have a mechanical strength sufficient for limiting warping of the plate which is otherwise caused by string tension. It is also required for a wooden frame to promote effective string vibrations through a sound board for balanced generation of tones from the bass to the treble range. Maintenance of sufficient strength is in particular important in order to keep standard string height, allow simple tone adjustment and maintain stable key touch over a long period.
A curved frame is a basic element in construction of a wooden frame and generally includes a straight bass range section and a curved treble range section. These sections have different rigidities due to difference in configuration. That is, since a curved section is inherently more rigid than a straight section, the rigidity of the straight bass range section is in general less than that of the curved treble range section. Since these two sections are same in height and thickness for convenience of in production, no configurational factors can make up for this difference in rigidity. As a result, the bass range section is inferior in tone volume and tone quality, thereby preventing balanced generation of beautiful tones over entire tone ranges.
In some conventional prior art frames, lamination of thin wooden plates is employed in the production of a curved frame of a wooden frame because of its excellent workability. For example, low density thin wooden plates made of meranti or lauan are laminated with high density thin wooden plates made of matoa, beech tree or birch tree. After lamination, the laminated body is worked into the shape of a curved frame of a wooden frame. Although the laminated body itself has uniform rigidity over its entire length, bending of the laminated body produces differences in the rigidity between, the bass and treble range sections. Thus, the prior use of art's lamination has not avoided the problem of unbalanced tone generation due to difference in rigidity.